Tunisia furious as Libya fighting spills over border (VIDEO)

Fighting between forces loyal to embattled Libyan leader Muammar Gaddafi and rebels spilled over into Tunisia Thursday, infuriating the Tunisian government.

Gaddafi's forces drove rebels from an outpost near the western Libyan town of Wazen, shut off one of their supply lines and chased them across the border with Tunisia, the Wall Street Journal reports. The two sides exchanged artillery fire Thursday night near Wazen, causing more civilians to flee into Tunisia.

Tunisia authorities said they were furious with Gaddafi for the incursion by his forces as well as for the firing of Grad rockets across the border.

"Given the gravity of what has happened," a Tunisian Foreign Ministry statement said, as reported by Reuters, "the Tunisian authorities have informed the Libyans of their extreme indignation and demand measures to put an immediate stop to these violations."

Gaddafi's troops apologized after briefly crossing the border.

Rebels, who have been fighting Gaddafi's forces for the past two months, captured the strategic border post last week, enabling them to bring supplies into the country. The crossing between Dehiba in Tunisia and Wazen on the Libyan side has been critical because it serves as the only road link for Libya's rebels in the west with the outside world.

The wave of protests that have swept the Arab world began in Tunisia, leading to the overthrow of President Zine al-Abidine Ben Ali in January.

Meanwhile, Gaddafi's forces have intensified their assault on Misurata, the city in western Libya that has seen some of the worst fighting.

And a NATO air strike Wednesday reportedly killed at least 11 rebel fighters in Misurata.